Marabou is one of the most popular materials for the tailing of lures. The material is very simple to tie in but if not prepared correctly can result in the fly's body being too bulky due the excess "fluff" from the marabou. These are some very basic step by steps that I use and will assist you in getting the best out of the marabou.
Grip the marabou stalk ends between your right hands thumb and index finger and run the thumb nail down the marabou. This should strip some of the fluff out. Repeat until most of the fluff has been removed and you are left with a thin profile.
Wet the thumb and index finger of your right hand and again grip the marabou stalk ends between your right hands thumb and index finger and run the marabou through them. This will cause the marabou to become wet and will give an even slimmer profile. Repeat until you are happy with the marabou's profile.